Recently retinoid analogs (vitamin A) have been shown to be potentially useful as cancer preventitives. The retinoids also play pivotal roles in the visual process as well as in the function of the purple membrane, the proton pump of Halobacterium halobium. The research involves the use of vinyl allene intermediates for synthesizing vitamin A as well as other target molecules. Besides being of interest as retinoid analogs in their own right, vinyl allenes can be thermally rearranged through a 1,5-sigmatropic shift of hydrogen to the 5,7,9,11,13-pentaene characteristics of the parent vitamin A system possessing an 11-cis on 9,11-dicis geometry. We propose to carry out studies in the following areas: (1) Application of the vinyl allene approach to the synthesis of 11-cis-and/or the unknown 9,11-cis,cis-retinals as well as other retinoids; (2) Examination of the Z yields E rearrangement of 11-Z-retinal and preparation of 11-Z-retinal with isotopic labels; (3) A scope study of the preparation and chemistry of vinyl allenes to further elaborate on the characteristics and limitations of the approach.